JP2014129186A - Ceramic slurry and method for producing the same, and solid oxide fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide ceramic slurry and its production method which can pulverize particles composing a ceramic layer, and a solid oxide fuel cell.SOLUTION: Ceramic slurry contains a dispersion medium and ceramic fine particles. The ceramic fine particles has an average particle diameter measured by dynamic light scattering of 100 nm or less, and are contained at 0.1 mass% or more. The ceramic slurry is obtained by crushing ceramic coarse particles using first ceramic balls in a first mixing step and crushing the ceramic coarse particles using second ceramic balls having an average particle diameter smaller than that of the first ceramic balls in a second mixing step.

Description

  The present invention relates to a ceramic slurry containing a dispersion medium and ceramic particles, a method for producing the same, and a solid oxide fuel cell.

  In recent years, research and development of fuel cells has been vigorously advanced. For example, a solid oxide fuel cell has high power generation efficiency because of its high operating temperature, and is highly expected as a cell for a third generation power generation system.

  Such a solid oxide fuel cell conventionally has, for example, a pair of flat surfaces parallel to each other, a fuel gas flow path for allowing fuel gas to flow inside, and containing Ni. One having a conductive porous support substrate is known. A fuel electrode layer, a solid electrolyte layer, and an oxygen electrode layer are stacked in this order on one main surface of the porous support substrate, and an interconnector layer is stacked on the other main surface.

  The fuel electrode layer and oxygen electrode layer are composed of fine particles in order to increase the three-layer interface and reaction surface area, and a porous structure including fine pores is required to supply gas to more particle surfaces. . The fuel electrode layer and the oxygen electrode layer are made of, for example, porous ceramics.

  The porous ceramic is formed by applying a slurry, in which ceramic particles and various additives are dispersed in a dispersion medium, to the surface of the substrate and performing a heat treatment. Ceramic particles are usually obtained by pulverizing large-sized coarse particles to obtain particles having a desired particle size.

  In the pulverization method described in Patent Document 1, the calcined powder subjected to the solid phase reaction is dispersed in an organic solvent or an aqueous solvent to form a high-concentration slurry, and pulverization media such as zirconia are mixed and pulverized. After pulverization, a material from which organic components and the like have been removed by heat treatment is used as a raw material powder, and a solvent is added thereto to obtain a slurry for producing porous ceramics.

In the pulverization method of Patent Document 1, BaTiO ₃ powder is contained in a container, and water, a dispersant, and ceramic balls having a particle diameter of 5 mm are added to obtain a raw material powder having an average particle diameter of 1 μm.

  Further, the method for producing particles described in Patent Document 2 includes mixing a plurality of organometallic salts, heat-treating them to remove organic components, reacting a plurality of metal ions to cause crystallization, and mixing and grinding. A powder is obtained, and an organic component is added thereto to produce a slurry.

JP-A-6-279094 JP 2004-216544 A

  However, in the slurry described in Patent Document 1, the average particle size of the ceramic particles in the slurry is 1 μm at most, and the ceramic particles dispersed in the slurry are large, and used as a raw material slurry for the fuel electrode layer and the oxygen electrode layer. In this case, the particle size of the ceramic layer is not reduced, and a porous structure with fine pores cannot be obtained.

  In addition, in the slurry described in Patent Document 2, in order to reduce the particle size of the raw material powder, it is necessary to lower the temperature at which the raw material powder is synthesized in order to suppress grain growth. There arises a problem that crystallization by metal ions is low. On the other hand, when the synthesis temperature is increased in order to increase the crystallinity, there is a problem that the particle size of the raw material powder increases.

  An object of the present invention is to provide a ceramic slurry, a method for producing the same, and a solid oxide fuel cell capable of miniaturizing particles constituting a ceramic layer.

The ceramic slurry of the present invention contains a dispersion medium and ceramic fine particles,
The ceramic fine particles have an average particle diameter measured by a dynamic light scattering method of 100 nm or less, and contain 0.1% by mass or more of the ceramic fine particles.

Further, the method for producing a ceramic slurry of the present invention includes a first mixing step of storing a mixture of ceramic coarse particles, a dispersion medium, and first ceramic balls in a container, and stirring the mixture in the container;
Second ceramic balls having an average diameter smaller than the first ceramic balls are accommodated in the container, the mixture containing the second ceramic balls is stirred, the ceramic coarse particles are pulverized, and measured by a dynamic light scattering method. And a second mixing step of producing a ceramic slurry in which ceramic fine particles having an average particle size of 100 nm or less are dispersed in a dispersion medium.

Furthermore, the solid oxide fuel cell of the present invention includes a solid electrolyte layer, an oxygen electrode layer disposed on one surface of the solid electrolyte layer, and a fuel electrode layer disposed on the other surface of the solid electrolyte layer. A fuel cell comprising:
The oxygen electrode layer is composed of ceramic particles made of LaCoO ₃ ceramics or LaFeO ₃ ceramics having an average particle diameter of 50 to 300 nm, and pores having a pore diameter in the range of 10 to 200 nm are 70% or more of the total pores It is characterized by being.

  According to the ceramic slurry of the present invention, the particles constituting the ceramic layer can be miniaturized by containing 0.1% by mass or more of ceramic fine particles having an average particle diameter of 100 nm or less.

  In addition, according to the method for producing a ceramic slurry of the present invention, the ceramic coarse particles aggregated using the first ceramic balls are crushed in the first mixing step, and the average is larger than the first ceramic balls in the second mixing step. By crushing the ceramic coarse particles using the second ceramic balls having a small diameter, a ceramic slurry in which ceramic fine particles having an average particle diameter of 100 nm or less are dispersed in a dispersion medium can be obtained.

Moreover, according to the solid oxide fuel cell of the present invention, the oxygen electrode layer is composed of ceramic particles made of LaCoO ₃ ceramics or LaFeO ₃ ceramics having an average particle diameter of 50 to 300 nm, and the pore diameter is 10 It is possible to provide a fuel cell in which pores in the range of ˜200 nm are 70% or more of the total pores. The reaction is promoted by increasing the reaction surface area in the oxygen electrode layer by decreasing the particle diameter of the particles constituting the oxygen electrode layer. Further, since small pores exist in the oxygen electrode layer, the supply of oxygen to the oxygen electrode / solid electrolyte surface smoothly proceeds and the reaction is promoted.

1 is a cross-sectional view showing a configuration of a solid oxide fuel cell 1. FIG. 2 is a photograph of a scanning electron microscope (SEM: 100,000 times) showing a cross section of an intermediate layer 5 and an oxygen electrode layer 6. It is a graph which shows the pore diameter distribution of an oxygen electrode layer. It is a graph which shows the polarization resistance in each temperature of an oxygen electrode layer.

<Ceramic slurry>
The ceramic slurry of the present invention contains a dispersion medium and ceramic fine particles, and the average particle size of the ceramic fine particles is 100 nm or less as an average particle size measured by a dynamic light scattering method, and the ceramic fine particles are It contains 0.1% by mass or more. Ceramic fine particles are dispersed in a dispersion medium.

  The dispersion medium in the ceramic slurry of the present invention (hereinafter sometimes simply referred to as slurry) may be any medium that can disperse ceramic fine particles, and for example, an organic solvent or water can be used. As the organic solvent, it is preferable to use methanol from the viewpoint that a solvent generally used for producing a ceramic slurry, for example, an alcohol solvent can be used and the dispersibility of the ceramic fine particles can be achieved. As the organic solvent, a cationic surfactant or the like can be further used for improving the dispersibility of the ceramic fine particles.

  The content of the ceramic fine particles in the ceramic slurry is 0.1% by mass or more. The content of the ceramic fine particles in the slurry is desirably 1% by mass or more, and the upper limit is 30% by mass or less, desirably 20% by mass or less, and particularly desirably 10% by mass or less. The suitable range of the content of the ceramic fine particles in the slurry is 1 to 20% by mass, desirably 1 to 10% by mass.

  The content of the ceramic fine particles is set to 0.1% by mass or more. When the content of the ceramic fine particles is less than 0.1% by mass, when a ceramic layer is produced using the slurry, for example, a plurality of slurries are used. This is because a predetermined thickness cannot be obtained unless it is applied twice, and the number of steps increases.

  Moreover, the average particle diameter of the ceramic fine particles dispersed in the slurry is 100 nm or less as an average particle diameter measured by a dynamic light scattering method. In the dynamic light scattering method, laser light is irradiated to particles such as ceramic fine particles dispersed in a liquid dispersion medium, and the scattered light is received by a photon detector arranged at a predetermined scattering angle. This is a method for measuring the average particle size and the particle size distribution from the autocorrelation function. The measurement range of the particle diameter by the dynamic light scattering method is 7 μm or less. The particle size measured by the dynamic light scattering method is the particle size of the particles dispersed in the dispersion medium. Therefore, the particle size of the ceramic fine particles alone and the particle size of the aggregated particles in which the ceramic fine particles are aggregated are included. It is.

  The measurement of the particle size by the dynamic light scattering method is defined as “particle size analysis-photon correlation method” in JIS Z8826, and the average particle size of the ceramic fine particles contained in the ceramic slurry of the present invention is in JIS Z8826. It is the average particle diameter measured by a compliant measuring method.

As the ceramic fine particles in the ceramic slurry of the present invention, fine particles containing LaCoO ₃ ceramics or LaFeO ₃ ceramics as constituent materials can be used. Examples of the material of the ceramic particles, the composite oxide forming the other oxygen electrode, for example may be an LaSrMnO _{3, further, CeO 2, ZrO 2, Fe} 2 O 3 _{to CeO} 2, Ga is dissolved Of course, Al ₂ O ₃ , NiO, Co ₃ O _{4 and the} like may be used.

<Method for producing ceramic slurry>
Next, the manufacturing method of the ceramic slurry of this invention is demonstrated. The production method of the present invention includes two mixing steps, a first mixing step and a second mixing step.

  In the first mixing step, ceramic coarse particles, a dispersion medium, and first ceramic balls are accommodated in a predetermined container, and the mixture thereof is stirred.

  The mixing ratio of the mixture in the first mixing step is, for example, 0.03 to 10% by mass of ceramic coarse particles, 55 to 75% by mass of first ceramic balls, and the remainder as a dispersion medium.

  The ceramic coarse particles are formed into ceramic fine particles by being crushed and pulverized through two mixing steps. The average particle diameter of the ceramic coarse particles is, for example, 0.3 to 1 μm. Further, the constituent material of the ceramic coarse particles is the same constituent material as the ceramic fine particles.

As the ceramic coarse particles, particles obtained by pulverizing the aggregates and pulverizing the particles are used which are heat-treated and calcined and synthesized. For example, for LaSrCoFeO ₃ , LaSrCoFeO ₃ , La ₂ O ₃ , SrCO ₃ , Co ₂ O ₃ , and Fe ₂ O ₃ powders are mixed and calcined and synthesized to form LaSrCoFeO ₃ that is a perovskite crystal. Get. After that, pulverization and pulverization are performed to obtain coarse ceramic particles having an average particle size of 0.3 to 1 μm. The average particle diameter can be obtained by taking an optical microscope photograph such as an SEM photograph and using the intercept method.

  Moreover, the dispersion medium accommodated in the container is used as a dispersion medium for the ceramic slurry. As the dispersion medium, it is preferable to use methanol from the viewpoint that a material generally used for producing a ceramic slurry, for example, an alcohol solvent can be used and the dispersibility of the ceramic fine particles can be achieved.

  As the first ceramic balls as the pulverization medium, generally, ceramic pulverized particles can be mixed and pulverized. In particular, zirconia-based ceramic balls having high strength and hardness can be used, but are not limited thereto. The average diameter of the first ceramic balls is, for example, 1 to 4 mm. The average diameter can be obtained by taking a micrograph and using the intercept method.

  The first mixing step is mainly a step of crushing the agglomerated ceramic coarse particles, and it is not necessary to crush the ceramic coarse particles, but a part of the ceramic coarse particles may be pulverized.

  In the first mixing step, for example, any stirring and mixing method may be used as long as the ceramic coarse particles can be crushed and pulverized, but it is preferable to stir the mixture by a planetary mill method. In the planetary mill method, a container containing the mixture rotates, and a large centrifugal force is generated by a planetary motion that the container revolves to stir and mix the mixture in the container. By using the planetary mill method, the aggregation of the ceramic coarse particles can be easily crushed by the collision between the aggregated ceramic coarse particles and the first ceramic balls. When the planetary mill method is used in the first mixing step, for example, under the conditions of a rotation speed of 300 to 2000 rpm, a rotation speed of 30 to 2000 rpm, a rotation / revolution ratio of 1 to 10, and a stirring time of 0.3 to 3 hours. Stir and mix.

  Next, the first ceramic balls are removed from the mixture containing the crushed ceramic coarse particles. The first ceramic balls are removed by sieving the mixture in the container with a mesh having a roughness that allows the ceramic coarse particles to pass but not the first ceramic balls, thereby removing the first ceramic balls remaining on the mesh. be able to.

  The second ceramic balls having an average diameter smaller than the average diameter of the first ceramic balls are added to the mixture after the removal of the first ceramic balls, that is, the mixture of the crushed ceramic coarse particles and the dispersion medium.

  In the second mixing step, a mixture containing the second ceramic balls, that is, a mixture of the crushed ceramic coarse particles, the dispersion medium, and the second ceramic balls is placed in a container, and the mixture is stirred. By the second mixing step, the ceramic coarse particles are pulverized, and the ceramic slurry of the present invention in which the ceramic fine particles having an average particle diameter measured by the dynamic light scattering method of 100 nm or less is dispersed in the dispersion medium is obtained.

  As the second ceramic balls used as the grinding medium in the second mixing step, generally, those capable of mixing and grinding ceramic coarse particles can be used. In particular, zirconia-based ceramic balls having high strength and hardness can be used, but are not limited thereto. The average diameter of the second ceramic balls is smaller than the average diameter of the first ceramic balls, for example, 0.02 to 0.07 mm. In the second mixing step, the ceramic coarse particles can be finely pulverized to fine particles having an average particle size of 100 nm or less by stirring using the second ceramic balls having a relatively small diameter.

  In the second mixing step, for example, any stirring and mixing method may be used as long as the ceramic coarse particles can be pulverized, but it is preferable to stir the mixture by a planetary mill method. By using the planetary mill method, the ceramic coarse particles can be pulverized by the collision between the crushed ceramic coarse particles and the second ceramic balls. When the planetary mill method is used in the second mixing step, the rotation speed is larger than that in the first mixing step and the stirring time is increased. For example, the rotation speed is 600 to 2000 rpm, the revolution speed is 60 to 2000 rpm, Stir and mix under conditions of a revolution ratio of 1 to 10 and a stirring time of 0.3 to 10 hours.

  Finally, the mixture containing ceramic fine particles having an average particle diameter of 100 nm or less is sieved with a mesh having a roughness that allows the ceramic fine particles to pass but not the second ceramic balls, thereby leaving the second ceramic balls remaining in the mesh. And a ceramic slurry in which ceramic fine particles are dispersed in a dispersion medium is obtained.

  In the production method of the present invention, the aggregated ceramic coarse particles are pulverized in the first mixing step, and the ceramic coarse particles are dispersed in the dispersion medium, whereby a mixture suitable for pulverization is obtained and the pulverization efficiency can be increased. . In the second mixing step, a slurry in which 0.1% by mass or more of highly crystalline ceramic particles having an average particle diameter of 100 nm or less are dispersed can be obtained by applying large pulverization energy to the ceramic coarse particles. When heat treatment is performed at a high temperature, grain growth occurs and the particle diameter increases, but ceramic particles with high crystallinity are obtained. In the present invention, since the highly crystalline coarse particles treated at high temperature are pulverized, ceramic fine particles having high crystallinity can be obtained. The crystallinity of the ceramic particles can be confirmed by the half-value width of the main peak by an X-ray diffractometer (XRD).

  As a stirring and mixing method, for example, a rotating mill may be rotated at a relatively high speed in addition to the planetary mill method as long as large pulverization energy can be obtained. In the second mixing step, it is necessary to apply large pulverization energy to the ceramic coarse particles, and therefore it is desirable to use the planetary mill method.

  In the above-described method for producing a ceramic slurry, after the first mixing step using the first ceramic balls, the second ceramic balls are mixed in the second mixing step. You may perform the 3rd mixing process mixed with the 3rd smaller ceramic ball. By performing such a third mixing step, the average particle size of the ceramic fine particles can be further reduced.

  In the above embodiment, the second ceramic ball is added after removing the first ceramic ball in the second mixing step. However, the second ceramic ball is added without removing the first ceramic ball. Can also be crushed.

<Solid oxide fuel cell>
A solid oxide fuel cell produced using the ceramic slurry of the present invention will be described.

  FIG. 1 is a cross-sectional view showing a configuration of a solid oxide fuel cell 1. A solid oxide fuel cell (hereinafter sometimes simply referred to as a fuel cell) 1 has a configuration in which a plurality of layers are laminated as shown in FIG. 1, and an intermediate surface is formed on one main surface of the solid electrolyte layer 4. The oxygen electrode layer 6 is disposed via the layer 5, and the fuel electrode layer 3 is disposed on the other main surface of the solid electrolyte layer 4. The solid oxide fuel cell 1 may be in any form as long as it is a solid oxide fuel cell, such as a flat plate fuel cell, a hollow flat plate fuel cell, and a cylindrical fuel cell.

The oxygen electrode layer 6 is a porous layer composed of ceramic particles made of LaCoO ₃ ceramics or LaFeO ₃ ceramics having an average particle diameter of 50 to 300 nm, and pores having a pore diameter in the range of 10 to 200 nm 70% or more of all pores.

The fuel electrode layer 3 causes an electrode reaction and is preferably formed of porous conductive ceramics. For example, it can be formed from ZrO _{2 in which a} rare earth element is dissolved or CeO _{2 in} which a rare earth element is dissolved, and Ni and / or NiO. As rare earth elements to be dissolved in ZrO ₂ or CeO ₂ , Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu are used. Y and Yb are preferable because they can be used and are inexpensive. The fuel electrode layer 3 can be formed from, for example, ZrO ₂ (YSZ) in which Y is dissolved, and Ni and / or NiO.

The content of stabilized ZrO ₂ or stabilized CeO _{2 in} the fuel electrode layer 3 is preferably in the range of 35 to 65% by volume with respect to the entire fuel electrode layer 3, and the content of Ni or NiO is 65 to 35% by volume is preferable. Further, the porosity of the fuel electrode layer 3 is 15% or more, preferably in the range of 20 to 40%, and the thickness thereof is 1 to 30 μm. The porosity can be calculated by binarizing a cross-sectional SEM photograph and using image analysis software (ImageJ).

The solid electrolyte layer 4 is preferably made of a dense ceramic made of partially stabilized or stabilized ZrO ₂ containing 3 to 15 mol% of a rare earth element such as Y, Sc or Yb. As the rare earth element, Y is preferable because it is inexpensive. Further, the solid electrolyte layer 4 is desirably a dense material having a relative density (according to Archimedes method) of 93% or more, particularly 95% or more in terms of preventing gas permeation, and a thickness of 5 to 50 μm. Preferably there is. The solid electrolyte layer 4 may be a solid electrolyte layer other than ZrO ₂ such as lanthanum gallate or ceria.

  The intermediate layer 5 strengthens the bonding between the solid electrolyte layer 4 and the oxygen electrode layer 6, and the reaction of the component of the solid electrolyte layer 4 and the component of the oxygen electrode layer 6 forms a reaction layer with high electrical resistance. It is formed for the purpose of suppressing this. In addition, since the intermediate layer 5 is not an essential configuration, it is not always necessary to provide it.

Here, the intermediate layer 5 can be formed, for example, with a composition containing Ce and another rare earth element other than Ce. For example, (CeO ₂ ) _1-x (REO _1.5 ) _x ( In the formula, RE is at least one of Sm, Y, Yb, and Gd, and x preferably has a composition represented by 0 <x ≦ 0.3. Furthermore, it is preferable to use Sm or Gd as RE from the viewpoint of reducing electric resistance, for example, it is preferably made of CeO ₂ in which 15 to 25 mol% of SmO _1.5 or GdO _1.5 is dissolved. .

The oxygen electrode layer 6 is preferably at least one of LaFeO ₃ -based ceramics or LaCoO ₃ -based ceramics, and LaCoO ₃ -based ceramics are particularly preferable from the viewpoint of high electrical conductivity at a fuel cell operating temperature of about 600 to 1000 ° C. In the perovskite oxide described above, Fe or Mn may exist together with Co at the B site.

  Further, the oxygen electrode layer 6 needs to have gas permeability. Therefore, the porosity of the oxygen electrode layer 6 is preferably 20% or more, particularly preferably in the range of 30 to 50%. Furthermore, the thickness of the oxygen electrode layer 6 is preferably 30 to 100 μm from the viewpoint of current collection. The porosity can be calculated by binarizing a cross-sectional SEM photograph (100,000 times) and image analysis using image analysis software (ImageJ).

The oxygen electrode layer 6 is composed of LaCoO ₃ ceramic particles or LaFeO ₃ ceramic particles having an average particle diameter of 50 to 300 nm, and pores having a pore diameter in the range of 10 to 200 nm are 70% or more of the total pores. It is.

  The ratio (%) of pores having a pore diameter of 10 to 200 nm is the abundance (%) of the pore diameter of 10 to 200 nm with respect to all pores in the pore diameter distribution described later, and the pore diameter distribution curve and frequency 0%. A pore diameter distribution curve, a straight line with a frequency of 0%, a straight line parallel to the vertical axis indicating a pore diameter of 10 nm, and a vertical axis indicating a pore diameter of 200 nm, for the entire area surrounded by the straight line It is indicated by the ratio of the area surrounded by the straight line.

  FIG. 2 is a photograph of a scanning electron microscope (SEM: 100,000 times) showing a cross section of the intermediate layer 5 and the oxygen electrode layer 6.

  From the micrograph, it can be seen that the oxygen electrode layer 6 is composed of aggregated ceramic particles, and the gap between the particles becomes pores and exhibits gas permeability.

  The oxygen electrode layer 6 is obtained by applying the ceramic slurry of the present invention once or a plurality of times to the surface of the intermediate layer 5 and performing a heat treatment.

・ Production of ceramic slurry (first mixing step)
In a zirconia container having a volume of 45 ml, 1.5% by mass of La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ (LSCF) powder (average particle diameter 0.6 μm) as ceramic coarse particles. In addition, 27% by mass of methanol as a dispersion medium and 71.5% by mass of ZrO ₂ balls having an average diameter of 2 mm as first ceramic balls were mixed, and the mixture in the zirconia container was put into a planetary mill (P-7: manufactured by FRICH). Then, stirring was performed under the conditions of a rotation speed of 1000 rpm, a rotation speed of 500 rpm, a rotation / revolution ratio of 2, and a stirring time of 1 hour, and the ceramic coarse particles were crushed in a dispersion medium.

(Second mixing step)
The ZrO ₂ balls as the first ceramic balls are removed with a sieve, and 71.5% by mass of ZrO ₂ balls having an average diameter of 0.05 mm as the second ceramic balls are added to the crushed ceramic coarse particles and the dispersion medium. The mixture was added and stirred using the planetary mill under the conditions of rotation speed 1600 rpm, revolution speed 800 rpm, rotation / revolution ratio 2 and stirring time 1 hour.

Finally, the ZrO ₂ balls as the second ceramic balls were removed with a sieve to obtain a slurry in which 5% by mass of the pulverized ceramic fine particles were dispersed in the dispersion medium. The average particle size of the ceramic fine particles in the slurry was 30 nm as measured by a dynamic light scattering method in accordance with JIS Z8826.

  The slurry obtained as described above was prepared as Sample No. As shown in Table 1, the production conditions were changed and Sample No. 2-9 slurries were produced.

  Sample No. 3 and sample no. 9 is a comparative example, and sample No. 1, 2, 4 to 8 are examples.

  Sample No. of Comparative Example 3 used ceramic balls having the same average diameter as in the first mixing step in the second mixing step, and the average particle size of the ceramic fine particles in the slurry was 200 nm. Sample No. of Comparative Example In No. 9, the second mixing step was not performed, the first mixing step was performed for 24 hours, and the average particle size of the ceramic fine particles in the slurry was 600 nm. In either case, the ceramic coarse particles were not sufficiently pulverized, and ceramic fine particles having an average particle size of 100 nm or less were not obtained.

  Sample No. of Example In 1, 2, 4 to 8, ceramic fine particles having an average particle diameter of 100 nm or less were obtained.

· On one main surface of the solid oxide fuel cell fabrication Y ₂ O ₃ consisting of 8 mol% solid solution was stabilized _ZrO 2 (YSZ) solid electrolyte layer, _CeO 2 was dissolved the Gd 20 mol% ( An intermediate layer made of GDC) was formed, and a fuel electrode layer made of Ni and YSZ was formed on the other surface. Thereafter, the ceramic slurry shown in Table 1 is applied to one main surface of the intermediate layer and dried repeatedly, and heat-treated at 700 ° C. to form an oxygen electrode layer having a thickness of 50 μm. A fuel cell was obtained.

  For the oxygen electrode layer, the average particle size of ceramic particles, the proportion of pores having a pore size of 10 to 200 nm in all pores, the porosity, and the polarization resistance were evaluated.

  The average particle size of the ceramic particles constituting the oxygen electrode layer was obtained by taking a SEM photograph of a cross section, drawing a straight line of a certain length, obtaining the number of particles passing through the straight line, and dividing the certain length by the number. Calculated from the values (intercept method).

  The pore size distribution of the oxygen electrode layer was calculated by image analysis using image analysis software (ImageJ) after binarizing the SEM photograph (100,000 times) of the cross section shown in FIG.

  FIG. 3 is a graph showing the pore size distribution of the oxygen electrode layer. The horizontal axis indicates the pore diameter (μm), and the vertical axis indicates the frequency (%). G1 is sample No. which is an example. 1 shows the pore size distribution of the oxygen electrode layer produced using No. 1, and G2 shows the sample No. 1 as a comparative example. 9 shows the pore size distribution of the oxygen electrode layer produced using No. 9;

  G1 has an overall distribution on the small diameter side compared to G2, and sample No. The pore diameter of the oxygen electrode layer produced using Sample No. 9 can be seen to be smaller than the pore diameter of the oxygen electrode layer produced using No. 9.

  The ratio of the pores having a pore diameter of 10 to 200 nm to the total pores is the abundance (%) of the pore diameter of 10 to 200 nm with respect to all the pores in the pore diameter distribution, and the distribution curve of FIG. The distribution curve of FIG. 3, a straight line with a frequency of 0%, a straight line parallel to the vertical axis indicating a pore diameter of 10 nm, and a straight line parallel to the vertical axis indicating a pore diameter of 200 nm It calculated from the ratio of the area surrounded by.

  Sample No. which is a comparative example. 3 is 65%. The ratio of 9 is 30%, and all are less than 70%, and it can be seen that the pore diameter is distributed in a relatively large diameter.

  As shown in Table 1, sample No. It can be seen that the ratios of 1, 2, 4, 6, and 7 are all 70% or more, and the pore diameter is distributed in a relatively small diameter.

  The polarization resistance of the oxygen electrode layer was determined as follows. Using a potentiogalvanostat built-in frequency response analyzer (FRA), current is input to the cell and the impedance is obtained. In addition, a Naiquist plot was created by changing the frequency and obtaining the impedance spectrum, and the polarization resistance of the oxygen electrode layer was obtained by fitting with an equivalent circuit. The measurement conditions were an initial current of 0 mA and a current amplitude of 0.03 mA. In addition, since the temperature of the fuel cell at the time of electric power generation can change in 500-800 degreeC, the polarization resistance of the oxygen electrode layer was measured in each temperature atmosphere of 500 degreeC, 600 degreeC, 700 degreeC, and 800 degreeC.

FIG. 4 is a graph showing the polarization resistance at each temperature of the oxygen electrode layer. The horizontal axis indicates the reciprocal of temperature (K ⁻¹ ), and the vertical axis indicates polarization resistance (Ωcm ² ). L1 is sample No. which is an example. 1 shows the polarization resistance of the oxygen electrode layer produced using Sample No. 1, and L2 shows Sample No. as a comparative example. 9 shows the polarization resistance of the oxygen electrode layer produced using No. 9.

  In any temperature condition, L1 is lower than L2, and sample No. The polarization resistance of the oxygen electrode layer produced using Sample No. 1 It can be seen that it is lower than the polarization resistance of the oxygen electrode layer produced using 9.

1 solid oxide fuel cell 3 fuel electrode layer 4 solid electrolyte layer 5 intermediate layer 6 oxygen electrode layer

Claims (6)

Containing a dispersion medium and ceramic fine particles,
A ceramic slurry, wherein an average particle diameter of the ceramic fine particles measured by a dynamic light scattering method is 100 nm or less, and the ceramic fine particles are contained in an amount of 0.1% by mass or more. The ceramic slurry according to claim 1, wherein the ceramic fine particles are made of LaCoO ₃ ceramics or LaFeO ₃ ceramics. A first mixing step of storing a mixture of ceramic coarse particles, a dispersion medium, and first ceramic balls in a container, and stirring the mixture in the container;
Second ceramic balls having an average diameter smaller than the first ceramic balls are accommodated in the container, the mixture containing the second ceramic balls is stirred, the ceramic coarse particles are pulverized, and measured by a dynamic light scattering method. And a second mixing step of producing a ceramic slurry in which ceramic fine particles having an average particle diameter of 100 nm or less are dispersed in a dispersion medium.   In the second mixing step, after the first ceramic balls are removed from the container, the second ceramic balls are accommodated in the container, and the mixture containing the second ceramic balls is stirred. The method for producing a ceramic slurry according to claim 3.   5. The method for producing a ceramic slurry according to claim 3, wherein in the second mixing step, the mixture containing the second ceramic balls in the container is stirred by a planetary mill method. A fuel cell comprising a solid electrolyte layer, an oxygen electrode layer disposed on one surface of the solid electrolyte layer, and a fuel electrode layer disposed on the other surface of the solid electrolyte layer,
The oxygen electrode layer is composed of ceramic particles made of LaCoO ₃ ceramics or LaFeO ₃ ceramics having an average particle diameter of 50 to 300 nm, and pores having a pore diameter in the range of 10 to 200 nm are 70% or more of the total pores A solid oxide fuel cell characterized by the above.